William,
There is a book called Homes in the Heartland:Balloon Frame Farmhouses of the Upper Midwest, 1850-1920 that has a chapter on Settlement and Shelter. This chapter has a good-sized section on sod houses. See citation below
Peterson, Fred W.
1992 Homes in the Heartland:Balloon Frame Farmhouses of the Upper Midwest, 1850-1920. University Press of Kansas, Lawrence.
Holly P. Halverson
Archaeologist, BRW, Inc.
Minneapolis, MN 55415